1. Field of the Invention
Disclosed herein are systems and methods for making nanoparticles, more particularly non-spherical nanoparticles having globular, coral-like shapes.
2. Relevant Technology
Various processes used to produce nanoparticles are known in the art. The term “nanoparticle” often refers to particles of any shape having a largest dimension of less than 100 nm.
U.S. Pat. No. 5,585,020 discloses methods for making nanoparticles with an average diameter of 73 nm and a standard deviation of 23 nm). This method utilizes laser ablation of initial diameter target particles of less than 100 microns within an inert gas or vacuum system.
U.S. Pat. No. 7,374,730 discloses methods for making nanoparticles within an organic liquid medium and uses stabilizing agents, such as surfactants or coating agents or other hydrocarbon materials, to prevent coalescence or growth of nanoparticles.
U.S. Pat. No. 7,662,731 identifies a need to prevent oxidation during laser sputtering/ablation and carries out ablation in superfluid helium.
U.S. Pat. Pub. No. 2013/0001833 to William Niedermeyer teaches that spherical particles are highly desirable because of their uniform shape and repeatable characteristics and discloses an apparatus and process for creating spherical nanoparticles from a solid target using ablation and an electromagnetic field configured to produce spherical nanoparticles of controlled size and narrow particle size distribution.
Picosecond ablation is known and provides shorter pulses that reduce the time for ions to form and helps control size; however, the power output of picosecond ablation is relatively small, limiting the quantity of material produced with relatively small ablation material plumes.
Nanoparticles can be grown into spheres through chemical reduction methods (e.g., silica), while production of spherical nanoparticles from other starting materials has traditionally been through a two-step process. In a first step, growth of nanoparticles from non-silica starting materials by chemical reduction methods produces non-spherical shapes, such as hedrons, platelets, rods, and other non-spherical shapes. While these methods provide good control for size, the resulting non-spherical shapes require further processing before they can become spherical in shape. In a second step, laser ablation is used to aggressively mill the non-spherical particles into quasi-spherical and/or spherical shapes. This process often produces unwanted “scrap” pieces and metal ions as byproduct. The spherical particles are then filtered to remove the ions and unwanted scrap.